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Current Regulated Reference Diode

IP.com Disclosure Number: IPCOM000078484D
Original Publication Date: 1973-Jan-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Ellis, JJ: AUTHOR

Abstract

Voltage regulators commonly employ a zener diode reference to which voltage fed back from the output of the regulator is compared, for control of the regulator. The reference circuit may consist of the diode, in series with an impedance, across the regulator output. In such a case, any variation in the regulator output voltage results in variation in the current through the diode. This sometimes provides intolerable variation in the reference voltage across the diode.

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Current Regulated Reference Diode

Voltage regulators commonly employ a zener diode reference to which voltage fed back from the output of the regulator is compared, for control of the regulator. The reference circuit may consist of the diode, in series with an impedance, across the regulator output. In such a case, any variation in the regulator output voltage results in variation in the current through the diode.

This sometimes provides intolerable variation in the reference voltage across the diode.

A more stable reference can be provided by powering the zener reference diode through its own regulator. V1 is a DC voltage which is the most stable available in the circuit environment, such as the output of the voltage regulator, not shown, which uses the output V2 - V3 across zener CR1 as its reference. Q1 provides current from V1 through R1 and zener diode CR1 for operation of CR1. This current is stabilized by the operation of a feedback circuit including divider R2 - R3 which provides a voltage V4. V4 is inputted to the operational amplifier which in turn provides base control to Q1. The parameters are chosen to yield the following: VR3 approx. = V2 - V3 VR2 approx. = VR1 IR1 approx. = R2 over R1R3 (V2 - V3).

The key performance of the circuit parameters are:

1) Temperature coefficient of CR1 determines the output stability limit for the reference.

2) The temperature coefficient and drift for R2/(R1.R3) is directly proportional to variations in IR1, which itse...